Switch mechanism with wire armature



C. C. RENNECAMP SWITCH MECHANISM WITH WIRE ARMATURE March 14, 1950 FiledDec. 4, 1946 T f 6 Z 9 M a Z 3 mm 5 a, 5 w a Patented Mar. 14, 1950SWITCH MECHANISM WITH WIRE ARMATURE Clarence C. Itennecamp, St. Louis,Mo., assignor, by mesne assignments, to Missouri Automatic ControlCorporation, a corporation of Missouri Application December 4, 1946,Serial No. 713,957

2 Claims.

This invention relates to switch mechanisms and more particularly toswitch mechanisms actuated by temperature or pressure responsive devicesand including magnetic means which acts to provide a snap action in bothclosing and opening movements of the switch.

In mechanisms of this character the relationship of the armature to themagnet when in an attracted position is extremely critical because itdetermines the minimum difl'erential in a condition which will cause theswitch to be moved from an open to a closed position and vice versa.

In the usual construction of armatures of'this type in which flatsurfaces of extended area are presented to a flat surface of the magnet,any slight non-parallelism or irregularity of the surfaces occurring inmanufacture, assembly or in adjustment will alter the magnetic pull antherefore the differential.

Because any variables due to such surface irregularities ornon-parallelism are greatly multiplied as the distance between armatureand magnet are decreased, it is customary to provide stops fordefinitely spacing the armature from the magnet when in its attractedposition.

'It is an object of the present invention to provide a new and improvedswitch mechanism adapted to economical and uniform manufacture.

A further object is to provide a switch mechanism incorporating animproved two direction magnetic snap action device having substantiallypoint contact between magnet and armature.

A further object is to provide a novel and imspherical contactingsurfaces spaced from the rial and has mounted thereon switch terminalconnectors 4 and I5. The connectors have riveted thereto flexible switchblades l5 and I1 respectively, which in turn carry contacts l8 and i9respectively. A cover fits over the frame Ill, its open side restingagainst the front plate members [i and I2.

Pivoted on a pin 2| which is supported in the side walls of frame memberIII are a differential lever 22 and a primary lever 23. Lever 22 has aforked outer end 24 extending between a fixed stop 25 and the adjustablecollar 26 on the threaded member 21. Lever 22 is further provided with aright angularly formed portion 28.

center of mass of the armature and arranged to alternately contact themagnet.

the following description and accompanying drawing referring to which:

Fig. 1 is a front view of a switch mechanism constructed in accordancewith the present invention.

Fig. 2 is a longitudinal section taken on line 2-2 of Fig. l.

Fig. 3 is a transverse section taken on line 33 of Fig. 1.

Figs. 4, 5 and 6 are enlarged detail views of the armature.

In the drawing reference numeral ill indicates a channel shaped framemember having attached thereto front plate members i l and I2.

The front plate members are attached to the channel frame by the fourpeened over projections l3. Plate member ii is of insulating mate- Thelever 23 also has a right angularly formed portion 29 at its outer end.Lever 23 is urged in a clockwise direction by actuation spring 30.

A secondary lever generally indicated at 3| is provided at one end withright angularly formed portions 32 and 33 parallel to the formedportions 28 and 29 of levers 22 and 23. Lever 3| is connected to levers22 and 23 by thin flexible strips 34 and 35. These strips 34 and 35perform the function of pivoted links and have the advantage ofeliminating any lost motion incident to the necessary tolerance infitting and journaling link pivots. Lever 3| includes an intermediateportion 35 of insulating material and a flexible free end portio 36a.

Lever 3| carries at its free end, an armature generally indicated at 31,preferably formed of round wire of magnetic material and having thegeneral shapepf a block letter S. A loop 38 formed at the end of theupper horizontal leg facilitates suitable attachment to the outer end oflever 3| by a bolt 39. A bar magnet 40 supported in an insulator block4| has one end pro- .jecting betweenthe intermediate and lowerhorizontal legs 42 and 43 of the armature. The magnet supporting block4| is attached to the base of frame l0 by inserted rivets 44.

In order to space the main mass of legs 42 and 43 from the magnet wheneither are in the attracted position, and in order to provide a fluxpath between the main mass of the armature legs and the magnet, a pairof inwardly formed V- shaped projections 45 and 46 are provided. Thepoints of the V's, 45 and 46 are rounded with a radius approximatelyequal to the diameter of the wire, resultin in a substantially sphericalpoint.

Lever 3| also carries at the outer end of its insulator section 35 ascrew 41 which under certain conditions bears against the outer end ofswitch blade ll thereby to open the contacts I I and II.

There is a stud ll extending thru an opening II in lever 22, an opening50 in lever 22, and an opening ii in the base of frame ll. Stud 4|threadedly engages an adjusting nut |2 at one end and at its oppositeend abuts the displaceable wall or diaphragm 52 of a solid charge typecondition responsive element generally indicated at N. Element 54further includes a rigid cup shaped member 5| having a flange H and acapillary tube 51 which communicates with a bulb (not shown) located inthe conditioned area. Element 54 is securely fastened to the base offrame In by screws 58. Cover member 2| and a mounting bracket 59 (shownin part) are also secured to the base of frame III by screws ll.

Adjusting nut 52 is guided for free axial and rotary movement in awasher H which i mounted in front plate l2, The outer end of nut 52 hasan indicator dial 50 attached thereto and a spring 6i having one endbearing against the end of stud 0 and its other end bearing against thenut 52 thru an intermediate washer 62 provides increased friction forretaining adjusted positions. The opposite or inner end of nut 52engages a pair of projections 62 on the primary lever 2|.

A return spring it having one end bearing against the base of frame Inand its other end against a collar 65 on stud I! normally urges the studand nut 52 toward the left (in the drawing) and therefore urges lever 22in a counterclockwise direction. Spring 64 is sufllciently stronger thanspring 30 to readily overcome. it.

Operation The switch mechanism shown in the drawings operates upon anincrease in temperature or expansion of the solid liquid charge in theelement 54 to close a circuit, as would be required in refrigerationservice wherein the closing of contacts Ill and I9 would complete anenergizing circuit for a compressor or the like. It will be notedhowever, that by simply switching the connections of the levers so thatangularly formed portion 33 of lever 3| is connected to lever 22 at 29and portion 32 is connected to lever 22 at 2| instead of the way shown,the mechanism would then operate to open a circuit upon an increase oftemperature as would be required for a space heating control.

As shown in the drawings the mechanism is in a circuit closing position,to which it is moved under the urging of spring 30 upon sufficientexpansion of element 54. The outer end of arm 3| is in its leftwardmostposition, Fig. 2, screw 41 having been moved leftward sufficiently topermit the closing of contacts I8 and I! by the spring action of switchblade IT. The outer end of lever 22 bears against the collar 26 ofdifferential adjusting screw 21 and horizontal leg 42 of the armature 31is in contact with magnet 40 thereby holding the outer end of arm Si bymagnetic force.

Upon a decrease in temperature resulting in a contraction of the solidliquid charge, return spring 64 will act to cause stud l8 and nut '52 tomove leftward following the movement of diaphragm 53. This movement willcause a counterclockwise rotation of lever 23 about its pivot 2i, and itwill carry with it the connected end of lever 3| and therefore the outerend of lever 22 until the outer end of lever 22 abuts the fixed 4 stop2| which is the limit of the adjustable lostmotion differential.

During this first phase of the switch opening movement, that Ls untilthe outer end of lever 22 abuts the stop 2|, the lever 21 pivots aboutthe ball point of armature leg 42. Continued decrease in temperature andtherefore further counterclockwise rotation of lever 22 after contacthas been made with stop 2| will'cause the connector strip 2| to flex,and as a result the outer free end of lever II, to swing toward theright. During this latter phase of the opening movement, however, anduntil a critical point is reached wherein the magnetic attraction of leg42 of the armature is overcome. it will be seen that energy is stored inthe flexible outer end portion Ila of lever II. This energy initiates asnap action of the outer end of arm II in a rightwardly direction andprovides a carry over to the point where leg 43 of the armature is movedinto a sumciently strong magnetic field to complete the openingmovement.

It is desirable in many types of service that the mechanism operate froma switch open to switch closed position upon a very slight change intemperature, often as slight a differential as 2 F. In the mechanismshown the resulting movement of stud 2| due to volume change of thesolid liquid charge for a temperature change of 2 F., would be betweenone and two thousandths (.001 and .002) of an inch. With this in view itwill be readily appreciated that even slight variations in the magnetand armature relationship from unit to unit will appreciably affect theuniformity of manufacture with respect to minimum operatingdifferential.

In the armature construction shown, slight lateral or longitudinaltilting with respect to the face of the magnet is not reflected in anymeasurable variation of operating differential. In this constructionthere is provided a rounded point contact between armature and magnetand a means for spacing the main mass of the magnet from the main massof the armature which lends itself admirably to uniform and economicalmanufacture. This spacing means being of magnetic material provides aflux path between the main mass of the armature and the magnet.

()bviously, numerous modifications of the principles of this inventionwill occur to those skilled in the art. For example, the magnet itselfmay be provided with projections having ends with reduced area forcontact with flat surfaces of an armature.

The exclusive use of all such modifications within the scope of theappended claims is contemplated.

I claim:

1. For use in a device of the class described, a movable armatureconstructed of round wire and having a portion thereof formed in ageneral U shape a bar magnet disposed between the parallel legs of saidU-shaped portion, each of said parallel legs havingan inwardly formed V-shaped projection adapted to contact said magnet as said armature legsare alternately moved toward it, whereby the main mass of said armatureportions are spaced from said magnet and whereby substantially pointcontact is made.

2. For use in a device of the class described, a movable armatureconstructed of round wire having the general form of a block letter 8, abar magnet disposed between the lower horizontal legs of said armature,the upper horizontal leg of said armature having an attaching eye formedat its open end, and each of said lower horizontal UNITED STATES PATENTSlegs having a. portion formed in a 'generalV- shape with its apex towardsaid magnet, whereby Number Name Date substantially point contact ismade between said 649,102 Flechtenmacher y 8, 1 0 magnet and saidarmature'as the lower horizontal 5 1,725,255 Claytor 1929 legs thereofare alternately moved toward said 1,946,261 Zupa 6, 1934 magnet.2,145,950 Persons Feb. 7, 1939 CLARENCE c, RENNECAMR 2,29 ,502 PersonsJuly 28, 1942 2,353,075 Rennecamp July 4, 1944 REFERENCES CITED 1

